BS EN 15063-1:2014 BSI Standards Publication Copper and copper alloys — Determination of main constituents and impurities by wavelength dispersive Xray fluorescence spectrometry (XRF) Part 1: Guidelines to the routine method BS EN 15063-1:2014 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 15063-1:2014 It supersedes BS EN 15063-1:2006 which is withdrawn The UK participation in its preparation was entrusted to Technical Committee NFE/34/1, Wrought and unwrought copper and copper alloys A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © The British Standards Institution 2014 Published by BSI Standards Limited 2014 ISBN 978 580 83960 ICS 77.040.20; 77.120.30 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2014 Amendments issued since publication Date Text affected BS EN 15063-1:2014 EN 15063-1 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM December 2014 ICS 77.040.20; 77.120.30 Supersedes EN 15063-1:2006 English Version Copper and copper alloys - Determination of main constituents and impurities by wavelength dispersive X-ray fluorescence spectrometry (XRF) - Part 1: Guidelines to the routine method Cuivre et alliages de cuivre - Détermination des éléments principaux et des impuretés par spectrométrie de fluorescence X dispersion de longueur d'onde (FRX) Partie : Lignes directrices pour la méthode de routine Kupfer und Kupferlegierungen - Bestimmung von Hauptbestandteilen und Verunreinigungen durch wellenlängendispersive Röntgenfluoreszenzanalyse (RFA) Teil 1: Leitfaden für das Routineverfahren This European Standard was approved by CEN on November 2014 CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels © 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref No EN 15063-1:2014 E BS EN 15063-1:2014 EN 15063-1:2014 (E) Contents Page Foreword Introduction Scope Principle Terms and definitions 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 Instrumentation Principles of X-ray fluorescence spectrometers X-ray tubes .8 Vacuum system Test sample spinner Filters Collimators of slits 10 Analysing crystals 10 Counters 11 Simultaneous and sequential Instruments 12 Sampling and test sample preparation 12 6.1 6.2 6.3 6.4 6.5 Evaluation methods 12 General 12 Dead time correction 12 Background correction 13 Line interference correction models 13 Inter-element effects correction models 13 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 Calibration procedure 14 General 14 Optimizing of the diffraction angle (2θ) 15 Selecting optimum conditions for detectors 15 Selecting optimum tube voltage and current 15 Selecting minimum measuring times 15 Selecting calibration samples 15 Selecting drift control and recalibration samples 16 Measuring the calibration samples 16 Regression calculations 16 Method validation (accuracy and precision) 16 9.1 9.2 9.3 9.4 Performance criteria 17 General 17 Precision test 17 Performance monitoring 17 Maintenance 17 10 Radiation protection 18 Annex A (informative) Example of calculating background equivalent concentration, limit of detection, limit of quantification and lower limit of detection 19 Annex B (informative) Example of calculating line interference of one element to another 21 Annex C (informative) Example of performance criteria obtained under repeatability conditions 22 Bibliography 23 BS EN 15063-1:2014 EN 15063-1:2014 (E) Foreword This document (EN 15063-1:2014) has been prepared by Technical Committee CEN/TC 133 “Copper and copper alloys”, the secretariat of which is held by DIN This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2015 and conflicting national standards shall be withdrawn at the latest by June 2015 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights This document supersedes EN 15063-1:2006 Within its programme of work, Technical Committee CEN/TC 133 requested CEN/TC 133/WG 10 “Methods of analysis” to revise the following standard: EN 15063-1:2006, Copper and copper alloys — Determination of main constituents and impurities by wavelength dispersive X-ray fluorescence spectrometry (XRF) — Part 1: Guidelines to the routine method This is one of two parts of the standard for the determination of main constituents and impurities in copper and copper alloys The other part is: EN 15063-2, Copper and copper alloys — Determination of main constituents and impurities by wavelength dispersive X-ray fluorescence spectrometry (XRF) — Part 2: Routine method In comparison with EN 15063-1:2006, the following changes have been made: a) Definition 3.1 and 3.2 modified; b) Clause modified; c) Editorial modifications have been made According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom BS EN 15063-1:2014 EN 15063-1:2014 (E) Introduction Wavelength dispersive X-ray fluorescence spectrometry (XRF) has been used for several decades as an important analytical tool for production analysis XRF is characterised by its speed and high precision over a wide concentration range and as the XRF-method in most cases is used as a relative method, the limitations are often connected to the quality of the calibration samples The technique is well established and most of the physical fundamentals are well known This guideline is intended to be used for the analysis of copper and copper alloys but it may also be applied to other materials BS EN 15063-1:2014 EN 15063-1:2014 (E) Scope This European Standard provides guidance on the concepts and procedures for the calibration and analysis of copper and copper alloys by wavelength dispersive X-ray fluorescence spectrometry Principle An appropriately prepared test sample is irradiated by an X-ray beam of high energy The secondary X-rays produced are dispersed by means of crystals and the intensities are measured by detectors at selected characteristic wavelengths Concentrations of elements are determined by relating the measured intensities of test samples to calibration curves prepared from reference materials Terms and definitions For the purposes of this document, the following terms and definitions apply 3.1 reference material RM material, sufficiently homogeneous and stable with respect to one or more specified properties which has been established to be fit for its intended use in a measurement process [SOURCE: ISO GUIDE 30:1992/Amd.1:2008, definition 2.1] 3.2 certified reference material CRM reference material characterized by a metrologically valid procedure for one or more specified properties, accompanied by a certificate, that provides the value of the specified property, its associated uncertainty, and a statement of metrological traceability [SOURCE: ISO GUIDE 30:1992/Amd.1:2008, definition 2.2] 3.3 test sample representative quantity of material for testing purposes 3.4 calibration samples series of certified reference materials or if not available, reference materials used for calibration 3.5 drift control samples series of homogeneous materials that contain all the elements which have been calibrated and that cover the low, mid and high points of the calibration range for each element, used to detect variations over time in these points Note to entry: Drift control samples can also be used for statistical process control (SPC) of the instrument 3.6 recalibration samples samples at both low and high points in the calibration ranges used to recalibrate the spectrometer Note to entry: These samples are measured during the calibration procedure and the intensities obtained are stored in the computer according to the manufacturer's instructions BS EN 15063-1:2014 EN 15063-1:2014 (E) Note to entry: evaluated No chemical analyses are necessary, but the homogeneity of these samples should be carefully 3.7 calibration process to establish the curve(s) by measuring and calculating the best fit of net intensities for elemental concentrations of a number of calibration samples 3.8 recalibration adjusting instrumental output to conform to the calibration Note to entry: To compensate for day to day instrumental variation, a set of recalibration samples are measured at the minimum low concentration and at a high concentration for each element (two-points recalibration) The measured intensities are compared to the initial measured intensities stored during the calibration procedure and the recalibration coefficients are calculated Calibration constants are not changed 3.9 reference measurements measurements carried out to determine intensities for reference materials Note to entry: Initial intensities for the reference materials are stored during the calibration procedure and the intensities are updated to compensate for day to day variations 3.10 spectral background background caused by radiation energy of a wavelength corrected for its position in the spectrum, but not directly related to the desired observation Note to entry: For a spectral line, spectral background may consist of other lines, bands or continuous radiation 3.11 background equivalent concentration concentration of analyte, which, when it is excited, provides a net intensity equal to the spectral background Note to entry: See Annex A 3.12 limit of detection minimum concentration at which the signal generated by a given element can be positively recognised with a specified confidence level above any background signals Note to entry: See Annex A 3.13 lower limit of detection calculated minimum concentration based on counting statistical error at which the signal generated by a given element can be positively recognised, with a specified confidence level, above any background signals Note to entry: See Annex A 3.14 limit of quantification smallest concentration that can be determined with a specified confidence level related to the limit of detection by a factor dependent on the method Note to entry: See Annex A BS EN 15063-1:2014 EN 15063-1:2014 (E) 3.15 sensitivity rate of change of signal with change in concentration Note to entry: See Annex A Sensitivity is expressed as counts per second percent, and derived by difference in signals between a sample with a high concentration and one with a low concentration divided by the difference in concentrations Instrumentation 4.1 Principles of X-ray fluorescence spectrometers The principles of two different X-ray fluorescence spectrometer concepts are shown in Figures and Each detail is described in the following sub-clauses Key Crystal Spinner Primary collimator Counter X-ray tube Secondary collimator Test sample Figure — Plane crystal spectrometer geometry, used in sequential instruments BS EN 15063-1:2014 EN 15063-1:2014 (E) Key Crystal Spinner Source slit Counter X-ray tube Detector slit Test sample Figure — Curved crystal spectrometer geometry, used in simultaneous instruments 4.2 X-ray tubes Two different types of X-ray tubes are used: side-window tubes or end-window tubes Table compares these two types More favourable measuring conditions are usually obtained for elements with a low atomic number (Z < 20) with an end-window tube due to the thinner window Different high purity elements such as Rh, Ag, W, Cr or Au are used as anode materials For analysing copper and copper alloys, rhodium is usually used as the anode material in a multipurpose tube as it provides good excitation conditions for all elements of interest If possible, the anode material should not be the same as the element to be determined Table — Comparison between end-window and side-window tubes Feature End-window tubes Side-window tubes Cooling Two cooling circuits a) Direct cooling with deionised water b) Indirect cooling with tap water One cooling circuit Direct cooling with tap water Window Slight thermal stressing: Thinner window Greater thermal stressing: Thicker window Service Life 20 000 h 000 h The applicability of common anode materials is summarised in Table BS EN 15063-1:2014 EN 15063-1:2014 (E) NOTE Normally the number of pulses (counts) is indicated as kilocounts per second (Kc/s) The dead time of the counters may have an effect from a pulse rate of approximately 10 pulses per second, however, higher pulse rates may be used if correction is applied The counters used register pulses at different intensities as a function of the energy of the X-ray radiation Therefore, specific pulses or energies may be filtered out by selecting an electronic “window” (Pulse Height Discriminator), as pulse height discrimination eliminates interference pulses 4.9 Simultaneous and sequential Instruments X-ray fluorescence instruments can be subdivided into two categories: simultaneous and sequential Simultaneous instruments have several fixed goniometers (channels) arranged around the test sample so that the individual element lines can be measured at the same time with the same excitation conditions Each channel is optimised for each element In sequential instruments, the user has the flexibility to optimise the measuring conditions independently for all selected elements and their backgrounds The goniometer can be set to a pre-defined angle (5° to 150°) and the excitation conditions can be optimised separately for all elements Simultaneous instruments are often used in a production environment where speed is important and the sample matrix is known In modern instruments sequential and simultaneous functions can be combined Sampling and test sample preparation Test sample preparation is a critical procedure The test sample required is a flat solid with a diameter of at least 25 mm, and thickness of at least mm, prepared from a sample obtained directly from a melt by pouring the liquid metal rapidly in an appropriately designed mould The test sample is prepared on a milling machine, without any other mechanical treatment (grinding, etc.) Chips or small pieces of pure copper may be transformed into a suitable test sample by remelting under an inert gas atmosphere followed by the same operations as above NOTE Remelting copper alloys will lead to losses of elements, e.g Zn, Be, Pb The measuring surface should be free of defects Evaluation methods 6.1 General Measure the intensities of secondary X-rays produced at the selected characteristic wavelengths and apply corrections as described in 6.2 to 6.5 6.2 Dead time correction The dead time τ, is a function of a type of counter and can be calculated from the following approximate relationship between the measured pulse rate n, and the corrected pulse rate, n0 n0 = n 1− τ × n (1) The dead time τ is generally around µs With current types of spectrometers, dead time losses are often compensated by means of a built-in correction circuit If this is not the case, they can be determined by repeatedly measuring the same test sample at a constant high voltage and with different current settings or by measuring the ratio of IKα/IKβ, which is constant 12 BS EN 15063-1:2014 EN 15063-1:2014 (E) The pulse rates determined are a linear function of the current as long as the dead time has no effect on the measurement The numerical value of τ, results from the reciprocal of the pulse rate at which a deviation from the linear function has been established 6.3 Background correction The background consists mainly of scattered X-rays from the tube For very low concentrations of determined elements (trace analysis), it is necessary to take the background into account, i.e to work with the net intensity As the background fluctuations from test sample to test sample may assume magnitudes in the range of the line intensities, the background radiation value has to be subtracted from the gross value measured 6.4 Line interference correction models The spectral line of the element to be determined can be overlapped by adjacent lines of other elements This leads to an increased measured value The increase is corrected by subtracting the interfering proportion from the measured value of the element to be determined Two correction methods are common: I K = I g − f1 × I st I K = I g − f × C st (2) (3) Here, IK and Ig are the corrected and measured intensities, f1 and f2 are the interference factors, and Ist and Cst represent the intensity and mass fraction in percent of the interfering element Software solutions to handle line interferences differ between manufacturers Only the net intensities (corrected for line overlap) are used in regression analysis but in some cases the line interferences are calculated within the regression analysis If possible, line interferences should be investigated separately There are several ways to this: — By measuring a set of binary samples where the concentration of the element of interest is zero or constant and the interfering element concentration is increasing, the interference factor can then be calculated — Plot the intensities for the element in question on the Y-axis and the intensities for the interfering element on the X-axis — Use the equation Y = AX + B to calculate the straight line The slope A corresponds to the interference factor, see, for example, Annex B 6.5 Inter-element effects correction models The result of the fluorescence produced inside the test sample by one of the other alloying or accompanying elements is that the intensity of the analysis line is either too low (absorption effect) or too high (secondary excitation) when measured There are two basic types of methods used for correcting these inter-elements effects: a) “Physical parameter” method (fundamental parameters) This method assumes that a series of physical magnitudes are known, generally only by the spectrometer manufacturer who informs the user about the correction coefficients In the model, the correction is made on the basis of the mass fraction, in percent, using the following equations: 13 BS EN 15063-1:2014 EN 15063-1:2014 (E) ci = ci × ( ∑α ij × c j ) (4) j ci = a0 + a1 × Ii + a2 × ( Ii )2 (5) where i is the index of the element to be determined; j is the index of the interfering element; ci is the mass fraction in percent (%) of the element i; ci is the apparent (uncorrected) mass fraction, in percent (%); α ij is the correction coefficient of element j for the mass fraction in percent (%) of element i; cj is the mass fraction in percent (%) of the element j; a0, a1, a2 is the regression coefficients (a2 is often evaluated as 0); Ii is the measured intensity of the element i The mass fraction, in percent (%), of unknown samples can be calculated according to Equation (4) using iteration methods that converge so well, that they can be truncated by the computer after a few steps (normally five) b) "Empirical coefficients" method The correction coefficients may be determined using a multi-variable regression method If the mass fractions in percent (%) are taken as the variables, then a model formally identical to the Equations (4) and (5) is obtained and its solution is identical to that of the "physical parameter" method If, however, the intensities of the interfering elements are used instead, as a basis for the regression calculation 1), the following correction equation is obtained [ ci = α + × Ii + × (I i ) × + ] ∑α j ij × Ij (6) In this case, in order to determine the mass fraction, in percent (%) of an element of an unknown sample, it is sufficient to insert the intensity of the element to be determined and that of interfering elements in the correct Equation (6) Calibration procedure 7.1 General Before proceeding to the calibration step, it is necessary to ensure that the instrument is fully optimised to avoid time-consuming mistakes In this clause some strategic advice is given Check this advice before performing any measurements In most cases the basic calibration is performed only once owing to the high stability of the technique 1) The multi-variable non-linear regression methods used here lead to a complex, redundant, non-linear equation system that can only be solved iteratively by computers using a numerical analysis methods With new types of equipment, the relevant software is generally supplied 14 BS EN 15063-1:2014 EN 15063-1:2014 (E) 7.2 Optimizing of the diffraction angle (2θ) Since the geometrical configuration is slightly different from one instrument to another it is good practice to experimentally determine the actual peak position for each element Choose a sample with a concentration of the element as high as possible 7.3 Selecting optimum conditions for detectors Follow the instructions in the user's manual for setting the detector high voltage Pulse High Distribution (PHD) settings (lower level and window) should be set experimentally by measuring samples with concentrations within the actual concentration ranges to be calibrated 7.4 Selecting optimum tube voltage and current Depending on the equipment used, it might be possible to increase the sensitivity and peak to a background ratio by modifying the tube voltage and current, especially for elements with a low atomic number 7.5 Selecting minimum measuring times The statistical error can be minimised by increasing the measuring time For practical reasons, the measuring time is fixed between 10 s and 100 s As a rule of thumb, select a measuring time so that the relative standard deviation (RSD) of the statistical error at a % level of the element concentration is at least less than 0,5 % and that a 10 % level or more, is less than 0,1 % RSD for the statistical error is calculated using the following equation: RSD = N × 100 % = RT × 100 % (7) where N is the number of counts (c); T is the measuring time, in seconds (s); R is the count rate (c/s) 7.6 Selecting calibration samples The number of samples should be as large as possible As a rule of thumb, there should be a degree of freedom of 30 for calculating a regression curve from the values corrected in accordance with Clause This means that for p samples and n individual measurements per sample, the requirement of the following equation should be met n × p − = 30 (8) When plotting the calibration curve, the measured intensities are regarded as the ideals That means that in a graph, the intensity values I are plotted on the ordinate, and the mass fraction values c in percent (%) on the abscissa Following the correction procedure in Clause 6, the regression function in the following equation is calculated I = f (c ) (9) The analysis function and evaluation curve used for determining the unknown mass fractions in per cent are obtained by performing the reverse function A software package for calculating theoretical coefficients is often included in XRF-instruments Otherwise, they can be calculated by the manufacturer Using these coefficients, the degrees of freedom will not be affected since they are treated as fixed constants The number of samples 15 BS EN 15063-1:2014 EN 15063-1:2014 (E) could then be reduced, since the only unknown factors are the line interferences, the slope and the background 7.7 Selecting drift control and recalibration samples Instrumental drift is checked by running drift control samples The instrument should be recalibrated as frequently as performance experience indicates To correct for instrumental drift, select at least two recalibration samples per element, one at the higher level of the concentration range and one at the lower For practical reasons, try to minimise the total number of recalibration samples for an analytical programme In order to attain better repeatability, the recalibration samples shall be protected against contamination and stored in a desiccator 7.8 Measuring the calibration samples Measure the calibration samples and, in order to get initial intensities for further recalibration stored, measure the recalibration samples according to the instrument user's manual Keep the time between measurements as short as possible in order to minimize the long term variation 7.9 Regression calculations To make the regression calculation, follow the calibration guideline in the instrument user's manual The criterion for evaluating the accuracy of the various correction methods is a reduction of the residual spread of the mass fractions, in percent (%), for the calibration samples around the analysis function The residual spread is the standard deviation for the residuals due to differences between reference values and values for samples within the calibration set determined by X-ray spectrometry: SD = ∑ ( c − c' ) n− p (10) where SD is the residual spread; c is the reference value, expressed as mass fraction in per cent (%); c' is the measured value, expressed as mass fraction in per cent (%); n is the number of calibration samples; p is the number of parameters determined by regression calculation (p = for a straight line) Method validation (accuracy and precision) Validation can be divided into three steps: 1) Calculate the limits of detection and the limits of quantification 2) Check that the method has no systematic errors by measuring a number of certified reference materials, not used in calibration, covering the calibrated concentration range 3) Calculate the repeatability (r) and the reproducibility within the laboratory (Rw) 16 BS EN 15063-1:2014 EN 15063-1:2014 (E) Performance criteria 9.1 General Before starting a calibration or measuring procedure, satisfactory performance of the instrument shall be demonstrated Precision of the instrument shall be checked according to the procedure in 9.2 at regular time intervals (every 3, or 12 months), after major repairs or whenever there is reason to suspect that the measuring conditions might have changed During routine measurements, SPC-diagrams (control charts) shall be used in regular performance checking, see 9.3 9.2 Precision test In order to check the precision of the instrument, a test sample shall be measured under repeatability conditions, in a period of h to h, and the measured intensities shall be stored The same test sample cup shall be used and not moved between measurements The relative standard deviations (RSDcal) for each element shall be calculated and compared with the relative statistical standard deviation (RSDstat) calculated by Equation (7) in 7.5 If all mechanical movements in the instrument are included during the measurements, assuming that the instrumental error is of the same order as the statistical error, RSDcal should be less than or equal to times the RSDstat If no mechanical movements are involved (simultaneous instrument), then RSDcal should be close to RSDstat An example of a precision test for a simultaneous instrument is given in Annex C 9.3 Performance monitoring It is common practice to use SPC-diagrams (control charts) in the regular checking of both the method and instrument performance (test sample preparation excluded) As a rule of thumb, corrective actions should be based on assessment of the control charts Automatic drift corrections based only on time intervals should not be used The time interval between measurements of the check samples should be based on the experience of the stability of the instrument Instrument performance should be checked at least every h 9.4 Maintenance In order to ensure the operation is as fault-free as possible, a series of checks and maintenance is necessary at regular intervals Table gives an example for a current type of apparatus Maintenance may be carried out by the equipment manufacturer or by specially trained laboratory personnel Performance monitoring and maintenance should be recorded systematically 17 BS EN 15063-1:2014 EN 15063-1:2014 (E) Table — Example of checks and maintenance work to be carried out on X-ray fluorescence spectrometers System part Cooling system Vacuum system Check interval weekly Water level, temperature, pressure resistance and connections Oil level, pressure during standby and measurement monthly — every months — Change oil — Flow detector — Check detector resolution and PHD settings — Scintillation detector — — Check resolution and PHD settings Mechanical parts Electronics generator Change or water filters clean Change dynamic stressed O-rings in the vacuum system and test sample transportation system Clean detector and change foil — Clean Test sample holders, test sample rotation and transportation system — — — — — and every year Check power supplies and clean air filters and fans 10 Radiation protection The X-ray fluorescence spectrometers commercially available are generally approved fully-protected apparatus This means that the user is not subjected to any radiation when operating the apparatus All apparatus are subject to specific official approval and acceptance conditions The person responsible for managing or supervising the operation of the X-ray equipment shall provide evidence of knowledge of radiation protection according to national regulations 18 BS EN 15063-1:2014 EN 15063-1:2014 (E) Annex A (informative) Example of calculating background equivalent concentration, limit of detection, limit of quantification and lower limit of detection Key BEC X Pb (%) Bg Y Kc/s Figure A.1 — Calibration curve for lead in copper-aluminium alloys Sensitivit y ( S ) = I High − I Low CHigh − CLow = 0,732 − 0,486 = 8,227 Kc/s % − 0,050 − 0,020 (A.1) IHigh, ILow, CHigh, CLow are taken from the curve Background Equivalent Concentration (BEC) = 0,038 % (absolute value in the curve) Background (Bg) = 0,32 Kc/s (from the curve) Measuring time (T) = 24 s (defined in the measuring programme) Relative standard deviation (RSD) on the background intensity = 1,1 % The RSD value is calculated based on data collected under reproducibility conditions within the laboratory, e.g different days, different operators and new test sample preparation Limit of detection (LOD) = × BEC × RSD = × 0,038 × 0,011 = 0,001 % 19 BS EN 15063-1:2014 EN 15063-1:2014 (E) Limit of quantification (LOQ) = × LOD = × 0,001 % = 0,003 % For practical reasons the LOQ is set to 0,004 %; measured values below 0,004 % should be reported as < 0,004 % Another equation for calculating the LOD is often referred in XRF literature In this guideline, that equation is used to define the lower limit of detection, LLD since it is based only on the counting statistical error The LLD is a very useful tool in comparing the performances of different XRF equipment Lower limit of detection (LLD) = 20 S Bg = 227 T 320 = 0,001 % 24 (A.2) BS EN 15063-1:2014 EN 15063-1:2014 (E) Annex B (informative) Example of calculating line interference of one element to another Select a set of samples with a low and constant content of an element A but with an increasing content of an element B Measure the A spectral line intensity and the B spectral line intensity Plot the intensities according to the following example: Int A = f (Int B) Key X Int B (c/s) Y Int A (c/s) Figure B.1 — Example for a plot of intensities Int A = f (Int B) Calculate the interference factor (f) = ∆IA 650 − 450 = = 0,036 ∆ I B 000 − 500 (B.1) Δ CB between points and is % in this case The difference in A intensities is about 200 c/s The sensitivity, S, for A is 8,400 Kc/s %-1 The influence of % B can be calculated by: % B = 0,006 % A 21 BS EN 15063-1:2014 EN 15063-1:2014 (E) Annex C (informative) Example of performance criteria obtained under repeatability conditions A test sample was measured 50 times, with a delay of 10 between the measurements No mechanical movements were involved except those of the test sample spinner The following results were obtained: Table C.1 — Performance criteria Performance criteria fulfilled Mean intensity RSDcal RSDstat Kc/s % % A 0,37 0,803 0,827 yes B 4,11 0,276 0,247 yes C 10,00 0,159 0,158 yes D 28,05 0,114 0,094 yes E 96,46 0,065 0,051 yes F 168,52 0,049 0,039 yes G 181,07 0,095 0,037 no Element The measurements were performed with a simultaneous instrument and the measuring time was fixed for all elements, 40 s The results obtained gave satisfactory relative standard deviation (RSDcal) for all elements except element G, which is more than two times higher than the statistical relative standard deviation (RSDstat), indicating a deficiency in that channel In such circumstances, the procedure should be investigated and repeated 22 BS EN 15063-1:2014 EN 15063-1:2014 (E) Bibliography [1] ISO GUIDE 30:1992/Amd.1:2008, Terms and definitions used in connection with reference materials; AMENDMENT 1: Revision of definitions for reference material and certified reference material [2] CRISS J.W., BIRKS L.S Anal Chem 1968 June, 40 (7) pp 1080–1086 [3] LUCAS-TOOTH J., PYNE C Advances in X-ray Analysis 1963, pp 523–541 [4] JENKINS R., DE VRIES J.L Practical x-ray spectrometry Springer, New York, 1970 [5] Quantitative X-Ray Spectrometry Second Edition, R Jenkins, R W Gould, Dale Gedcke, pg 48-50, 1995 [6] CR 10299, Guidelines for the preparation of standard routine methods with wavelength-dispersive X-ray fluorescence spectrometry 23 This page deliberately left blank This page deliberately left blank NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW British Standards Institution (BSI) BSI is the national body responsible for preparing British Standards and other standards-related publications, information and services BSI is incorporated by Royal Charter British Standards and other standardization products are published by BSI Standards Limited About us Revisions We bring together business, industry, government, consumers, innovators and others to shape their combined experience and expertise into standards -based solutions Our British Standards and other publications are updated by amendment or revision The knowledge embodied in our standards has been carefully assembled in a dependable format and refined through our open consultation process Organizations of all sizes and across all sectors choose standards to help them achieve their 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